In angle-measurement instruments,the mirror and rotary stage inevitably influence and often determine measurement accuracy.To clarify the systematic deviations introduced in the F-P etalon-based angle-measurement system,this article formulates a mathematical model describing micro-angle measurement errors caused by the mirror and the rotary stage,followed by a comprehensive analysis and correction.The model incorporates mirror pitch-angle error,initial zero-position angle error, eccentricity error,rotary-stage installation error, and rotation-axis eccentricity error.Through matrix operations and three-dimensional coordinate transformations, the displacement of the interference-ring center on the imaging plane under various errors is derived, forming a complete error-propagation framework. MATLAB is used to quantify the influence of each error source,examining cases with and without coupling.Results show that without coupling, the mirror eccentricity error dominates, whereas with coupling, principal component analysis (PCA) indicates that the mirror eccentricity error and initial zero-position angle error jointly exert the greatest impact. Based on this analysis, a targeted correction for mirror eccentricity is implemented. Within a measurement range of 1 800″, accuracy improves from ±1.93%FS to ±0.22%FS,reducing micro-angle measurement error by 91.9%. The effectiveness of the model and correction strategy is evaluated.